This week’s science column…


Edward Willett

Glow, little GloFish, glimmer, glimmer…

In January, a U.S. company hopes to offer for sale the first pet fish genetically engineered to glow under ultraviolet light.

This has alarmed some people, but scientists have been creating glowing organisms for several years now–and their ability to do so has revolutionized many fields of science.

Many creatures glow naturally, a phenomenon called bioluminescence. In the dark depths of the oceans, the majority do. But even though there are plenty of glowing fish in the seas, the zebra fish has never been one of them–until recently.

Researchers at the National University of Singapore injected the fish’s eggs with a gene that from a sea anemone which makes the anemone red, then added a jellyfish gene that causes cells to produce green fluorescent protein, or GFP, which glows green when hit by blue or ultraviolet light. The fish don’t glow all the time; instead, the production of GFP is linked to genetic switches in the fish that are activated by the presence certain toxins, such as estrogen. The goal isn’t to create a novelty pet, but a cheap and effective pollution detector. The researchers say the zebra fish could be made to fluoresce as many as five different colors, with each color activated by the presence of a different pollutant.

Both the Singapore scientists and Yorktown Technologies, the U.S. company that wants to sell the “GloFish” as pets, say they pose no hazard to the environment if they escape into the wild: not only are they tropical fish, unsuited to North American waters, but their fluorescence is actually a hindrance in the wild, requiring energy to maintain and making them more susceptible to predators (who wouldn’t be harmed by eating the fish–GFP is completely non-toxic).

The glowing fish have made the news, as did glowing green mice a few years ago and a glowing green bunny in 2000 (intended as art). But out of the limelight, many more organisms are glowing, making possible research that would otherwise be either difficult or impossible.

A Princeton scientist, Osamu Shimomura, discovered GFP in 1962 while studying a small bioluminescent jellyfish called Aequoria Victoria. Within the jellyfish, one protein, aequorin, glows blue in the presence of calcium. GFP, when struck by blue light, glows green, giving the jellyfish its overall green glow.

Almost 30 years later, Douglas Prasher, a researcher at the Woods Hole Oceanographic Institute, discovered the gene in jellyfish that coded for GFP. He ran out of funding before he could test the gene by inserting it into bacteria. That task fell to Columbia University professor Martin Chalfie. Most scientists assumed GFP would only glow in the presence of an enzyme or some other protein that only existed in the jellyfish. But they were wrong: when the GFP gene was put into bacteria and a blue light was shone on them, they glowed.

That’s what makes GFP such a powerful research tool. If scientists want to see if they have successfully inserted a gene into an organism, all they have to do is link it to GFP, then shine a light on the organism to see if it glows (although the glow is usually only detectable by highly sensitive cameras). GFP can also be linked to other proteins, allowing scientists to track the movement of specific proteins within a cell or organism.

GFP and other forms of bioluminescence are being used in hundreds of research projects today. The GFP gene, for instance, has enabled the study of adult stem-cells–those fabulous non-specific cells that can turn into the specialized cells required by all the body’s various systems. Stem cells taken from a mouse engineered to contain the GFP gene can be put into another mouse and their activity tracked by their glow.

Diseases like cystic fibrosis, AIDS and cancer can now be studied in greater detail than ever before. The progress of diseases in lab animals can be followed in real time using a sensitive camera, rather than interpolated after the fact by the results of dissection.

Of course, there are also more frivolous uses for bioluminescence–even more frivolous than glowing pet fish. A company called Prolume markets squirt guns that shoot glowing water and glowing “alien crystals”; future products touted at their Web site include glowing food (like a Bud Light that is really a Bud light) and glowing cosmetics.

Indeed, one can only say that the future of bioluminescence looks bright! (Sorry.)

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